1. Field of the Invention
The present invention relates generally to the preparation of polyurethane and polyisocyanurate polymers, and polymer foams from etherified modified aromatic polyols (low viscosity aromatic polyols) derived from digested polyols of the type made by the digestion of a polyalkylene terephthalate with a low molecular weight polyol such as ethylene glycol or diethylene glycol to provide a digested polyol, next reacting the digested polyol with a low molecular weight polyhydroxy compound having from about 3 to about 8 hydroxyl groups to provide an intermediate product and thereafter alkoxylating the intermediate product with ethylene oxide and/or propylene oxide to thereby provide an etherified modified aromatic polyol having improved physical properties. The etherified modified aromatic polyol has enhanced utility as a raw material for use in the manufacture of polyurethane foams and polyisocyanurate foams.
2. Description of the Prior Art
Polyurethane and polyisocyanurate polymers and polymer foams are formed by the reaction between an isocyanate and a polyol having at least two hydroxyl groups. For polyisocyanurate foams, the molar ratio of isocyanate to polyol will be greater than 1 to 1, usually equal to or greater than 2 to 1. Polyurethane and polyisocyanurate foams are produced by the reaction of the isocyanate and the polyol in the presence of a suitable blowing agent, surfactant and catalyst. The degree of rigid compressive strength or flexible load deflection is determined, in part, by the functionality and molecular weight of the isocyanate and the polyol.
Aromatic polyester polyols (digested polyols) useful for the production of polyurethane and polyisocyanurate foams can be derived from polyalkylene terephthalate polymers, such as polyethylene terephthalate (PET), and by digestion of the polymer with various low molecular weight aliphatic polyols, such as polyhydric alcohols.
The use of aromatic ester polyols obtained from polyalkylene terephthalate polymers for the preparation of polyurethanes and polyisocyanurates has a number of advantages. First, the polyalkylene terephthalate polymers can be obtained from scrap materials such as used photographic film, synthetic fibers, plastic bottles such as those used in the soft drink industry, and waste from the production of other products made from polyalkylene terephthalate polymers.
Despite these advantages, the results have not been entirely satisfactory. Polyols produced by digesting polyalkylene terephthalate polymers suffer from a number of disadvantages. The digestion products are highly viscous, typically having viscosities in the range from about 20,000 cps to solid at room temperature. Although the digested polyols can be blended with conventional polyols in order to lower the overall viscosity of the combined polyols, the resulting mixtures are not always stable and are susceptible to crystallization on storage. In addition, the digested polyols have limited solubility in fluorocarbon blowing agents and foams made therefrom can be dimensionally unstable. There is a need for a simple, yet flexible process for adjusting the physical and chemical properties of aromatic polyols so that the foregoing and related problems can be overcome and, in particular, so that different grades of aromatic polyols can be provided for specific end-use applications (e.g. low isocyanate index formulations, high isocyanate index formulations, rigid polyurethane formulations, rigid polyisocyanurate formulations, etc.).
Kaiser et al. U.S. Pat. No. 3,167,538 issued Jan. 26, 1965, discloses the preparation of polyols suitable for use in the manufacture of rigid polyurethane foam by alkoxylating a mixture of methyl glucoside with a polyhydric alcohol and an amino hydroxy compound. Kaiser et al. point out that when methyl glucoside is alkoxylated there are numerous problems because the methyl glycoside is a high melting solid which must be heated in order to become liquefied and suitable for alkoxylation. This tends to result in off color products which have excessive viscosities.
Schoepfle et al. U.S. Pat. No. 3,249,562 issued May 3, 1966, is directed to the preparation of polyurethane foam having improved fire resistance made by reacting a polyisocyanate with a polyester having a phosphinic acid. chemically combined therein.
Falkenstein et al. U.S. Pat. No. 4,035,313 issued July 12, 1977, is directed to polyisocyanurate foams having improved fire retardancy properties prepared by reacting a polyisocyanate and a polyester polyol containing N,N'-bis-(ethanol-2)-diaminooctachlorodiphenyl.
U.S. Pat. No. 4,048,104 to Svoboda et al. describes a method wherein an organic polyisocyanate, e.g., toluene diisocyanate is reacted with the digested polyol to form a prepolymer which is substantially free of unreacted hydroxyl radicals. The polyisocyanate prepolymer is then combined with additional polyol, a suitable blowing agent, a surfactant, and a catalyst in order to produce the desired flexible polyurethane.
U.S. Pat. No. 4,223,068 to Carlstrom et al. discloses the use of a digested polyol combined with a low molecular weight polyol in the production of rigid polyurethane foams. The amount of the digestion product present relative to the total organic polyol can be no more than 30% in order to retain the desired physical properties of the foam, particularly compressive strength and dimensional stability.
DeGuiseppi et al. U.S. Pat. No. 4,237,238 issued Dec. 2, 1980 discloses the preparation of polyisocyanurate foams having improved fire retardancy properties wherein the polyol that is used is a polyol prepared by the transesterification with a glycol of a residue obtained from the manufacture of dimethyl terephthalate.
Kolakowski et al. U.S. Pat. No. 4,039,487 issued Aug. 2, 1977, disclose polyisocyanurate foams having improved fire retardancy properties prepared by using, as a portion of the polyol component, a hydroxy terminated aromatic polyester prepared by reacting an excess of a polyethylene glycol with an aromatic polycarboxylic compound.
Satterly et al. U.S. Pat. No. 4,233,408 issued Nov. 11, 1980, discloses the manufacture of rigid polyurethane foam using a polyester polyol prepared by etherifying a waste stream of nonvolatile by-product from the oxidation of cyclohexane to cyclohexanone with a polyol.
Svoboda et al. U.S. Pat. No. 4,417,001 issued Nov. 22, 1983, discloses isocyanurate foam prepared from a polyol prepared by digesting polyalkylene terephthalate residues with organic polyols.
Brennan U.S. Pat. No. 4,439,549, which issued Mar. 27, 1984, on the basis of a patent application filed November 22, 1982, is directed to aromatic polyols containing ester functionalities suitable for use in making rigid polyurethane foam. The aromatic polyols are prepared by reacting a polyethylene terephthalate residue with an alkylene oxide in the presence of a basic catalyst.
Zimmerman et al. U.S. Pat. No. 4,442,237, which issued Apr. 10, 1984 on the basis of a patent application filed Nov. 22, 1982, is directed to aromatic polyols suitable for use in manufacturing rigid foam. The aromatic polyols are prepared by reacting a phthalic acid residue such as a residue from the manufacture of polyethylene terephthalate with an amino alcohol containing at least one tertiary amino group and at least one hydroxyl function and also with an alkylene glycol such as ethylene glycol or diethylene glycol. There is a statement that it is expected that useful novel aromatic polyol mixtures may be made with polyethylene terephthalate (PET) in place of the DMT residue used in the first step.
Zimmerman et al. U.S. Pat. No. 4,442,238, which issued Apr. 10, 1984 on the basis of a patent application filed Nov. 22, 1982, is directed to an aromatic polyol prepared by reacting a phthalic acid residue with an amino alcohol. The reaction product is subsequently alkoxylated.
The amino alcohol that is reacted with the residue is an amino alcohol containing a primary or secondary amine group and a hydroxyl group.
Grigsby et al U.S. Patent No. 4,469,824, which issued Sept. 4, 1984, discloses a polyol useful in the production of polyurethane foam which is prepared by digesting recycled polyethyelene terephthalate with diethylene glycol and at least one other oxyalkylene glycol in the optional presence of a minor amount of a functionality-enhancing additive such as alpha methyl glucoside, glycerine, triethanolamine, sorbitol, etc.